Pressure-sensitive record material

ABSTRACT

THIS INVENTION RELATES TO PRESSURE-SENSITIVE RECORD MATERIAL COMPRISING SUBSTRATE SHEET MATERIAL SUPPORTING PRESSURE-RUPTURABLE MARKING-LIQUID-CONTAINING CAPSULES SUFFICIENT IN NUMBER AND LIQUID CONTENT TO YIELD A VISUALLY CONTINUOUS IMAGE PATTERN WHEN RUPTURED BY A PATTERN OF IMAGE MARKING PRESSURE, SAID CAPSULES BEING ARRANGED IN THE RECORD MATERIAL IN APPOSITION TO SOLID CO-REACTANT MATERIAL WHICH, ON CONTACT WITH THE LIQUID, FORMS AN INTENSELY-COLORED REACTANT SLUDGE OF NEUTRAL HUE, THE INVENTIVE MERIT BEING THAT THE LIQUID CONTENTS OF THE CAPSULES IS A SINGLE LIQUID COMPOUND OR MIXTURES OF LIQUID COMPOUNDS WITHOUT DILUENT OR DISPERSANT, EVERY MOLECULE OF THE LIQUID   CAPSULE CONTENTS BEING REACTIVE WITH THE AVAILABLE SOLID MATERIAL TO PRODUCE THE SLUDGE-LIKE MARK.

Jan. 26, 1971 P. s. PHILLIPS, JR

PRESSURE-SENSITIVE RECORD MATERIAL Filed April 1, 1968 AUTOGENOUS SYSTEMS METAL SALT LIQUID N,N'- DISUBSTITUTED DITHIOOXAMIDES IN CAPSULES ANY SHEET SUBSTRATE- r FIBROUS SHEET (PAPER) LIQUID IN CAPSULES METAL SALTS, REACTIVE WITH THE LIQUID I ANY SHEET SUBSTRATE FIBROUS SHEET (PAPER) SUBSTRATE LIQUID DITHIOOXAMIDE COMPOUND NY SHEET SUBSTRATE I FIBROUS SHEET (PAPER) SUBSTRATE MULTIPLE SHEET SYSTEMS OVER SHEET CAPSULES LIQUID CAPSULE CONTENTS INVENTOR PAUL S. PHILLIPS, JR.

HIS ATTORNEY Unite States Patent 3,558,341 PRESSURE-SENSITIVE RECORD MATERIAL Paul S. Phillips, Jr., Dayton, Ohio, assrgnon to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed Apr. 1, 1968, Ser. No. 717,568 Int. Cl. B41m 5/22 US. Cl. 117-36.2 8 Claims ABSTRACT OF THE DISCLOSURE This invention relates to pressure-sensitive record ma terial comprising substrate sheet material supporting pressure-rupturable marking-liquid-containing capsules sufficient in number and liquid content to yield a visually continuous image pattern when ruptured by a pattern of image marking pressure, said capsules being arranged in the record material in apposition to solid co-reactant material which, on contact with the liquid, forms an intensely-colored reactant sludge of neutral hue, the inventive merit being that the liquid contents of the capsules is a single liquid compound or mixtures of liquid compounds without diluent or dispersant, every molecule of the liquid capsule contents being reactive with the available solid material to produce the sludge-like mark.

A color efficiency of high order is obtained by the provision of total reactivity of the capsule contents, the nature of the reaction product being a sludge and not prone to bleeding and feathering by reason of capillary and other surface forces, as is the case with many systems heretofore known, where solvent-diluted reactants are released from microcapsules onto paper substrates. In systems where the support sheet material may be paper of different grades of porosity, this non-bleed characteristic is of importance.

RELATED PRIOR ART There are many previous disclosures of pressure-sensitive sheet systems which are self-marking (autogenous) by reason of pressure-rupturable capsules being intermixed with or in apposition to co-reactant material in the same sheet or which are based on multiple sheets where the capsules are on an over-sheet and transfer released liquid to a sensitized undersheet.

A typical transfer system employing capsules of microscopic size, containing liquid of marking potentiality, which liquid is released from the capsules by marking pressures onto another sheet, is disclosed in United States Pat. No. 2,712,507, which issued July 5, 1955, on the application of Barrett K. Green, and in United States Pat. No. 2,730,456, which issued January 10, 1956, on the application of Barrett K. Green and Lowell Schleicher, although such disclosures were preceded in the art by an emulsion type of transfer coating containing discrete liquid droplets, as shown in United States Pat. No. 2,374,- 862, which issued May 1, 1945, on the application of Barrett K. Green. The capsule coating is preferred as more rugged. In those cases, a dilute solution of colorreactant material was employed. Many versions of such transfer sheet record material have intervened, all of which depended on the release of confined droplets of colorreactant materialbut in low concentration in some liquid solvent or dispersant.

A typical autogenous record material system, earlier sometimes referred to as self-contained because all the elements for making a mark were in a single sheet, is disclosed in United States Pat. No. 2,730,457, which also issued Jan. 10, 1956, on the application of Barrett K. Green and Lowell Schleicher. In that system, the color reactant was highly diluted by a solvent.

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It is thought that no one until this time has developed a system wherein the capsule contents, or isolated droplets which are to be released on the application marking pressures, was a liquid which was entirely a liquid compound reactant or mixtures of such liquid reactants and thus wholly reactive. The efiiciency of such a system is such that fewer capsules need be used to gain a commercially acceptable print. This not only is an economic advance in the art, but aesthetically improves the feel and handle of the sheet by having less foreign matter attached thereto or incorporated therein. Prints made with the novel system are bleed-proof or feather-proof, as the reaction product of the color reactants will not flow as a printed mark, being sludge-like.

SUMMARY OF THE INVENTION The system uses, for the capsule contents, in the preferred embodiment, those symmetrical N,N disubstituted dithiooxamides in which the substituents are saturated and unsaturated acyclic hydrocarbon monovalents radicals which are liquid at the temperature of the normal habitat of man in temperate climates. Eligible symmetrical materials for use in the capsules and which are water-immiscible, so as to be dispersible as droplets in water and encapsulated by conventional methods using agitated aqueous coacervation of solutions of hydrophilic film-forming polymeric material to enwrap droplets of the reactant material, among many, are:

Freezing point C. (I) N,N' dihexyl dithiooxamide 13 (II) N,N dipentyl dithiooxamide 7 (III) N,N dipropyl dithiooxamide 13 (IV) N,N' dioctyl dithiooxamide 9-105 (V) N,N' dioleyl dithiooxamide 7 Where the prevailing temperatures are low, a selection is made according to the freezing point. Mixtures of the reactant liquid compounds may be used for a blend of characteristics.

All these materials may be classed as fully operative materials, but I through IV have some vapor pressure leakage through the capsule walls, according to the temperature, that, speaking in terms of days, will cause discoloration of sensitized receiving sheets which may be held for storage in close contact therewith. Compounds I through IV are classed as N,N dialkyl dithiooxamides, whereas compound V is classed as a dialkenyl dithiooxamide compound and has no vapor pressure problem in storage against a sensitizing material (say, at 25 degrees centigrade) and is useful for pre-made forms comprising a capsule-bearing sheet held in contact relation with a receiving sheet sensitized with a co-reactant. It is also more useful for autogenous sheets which are to be held in storage. Capsules holding compounds I through IV may be made with a second coating that will preclude the casual passage of vapor to a closely-present reactant. Such capsules may be dispersed in an organic solvent solution of polymeric solution (say, of ethyl cellulose) and coated as any particle is by liquid-liquid-phase-separation practices as set forth in British Pat. No. 931,148. Some asymmetrical di-substituted dithiooxamide compounds too are eligible if they are liquid at the specified temperatures with the specified dithiooxamides.

The sensitizing solid materials eligible for use may be selected from the following group: Ni-dinoylnaphthalene sulfonate Cu-resinate Ni-resinate Cu-di(2 ethylhexyl) phosphate Ni-di (2 ethylhexyl) phosphate Ni stearate Mixtures of these salts may be used.

3 THE DRAWING The drawing shows, in FIG. 1, a diagrammatic rendition of six systems, [I] through [VI], which provide an autogenous sheet wherein the liquid-containing capsules and the solid material reactant therewith are provided, supported by the same base sheet of record material, and shows, in FIG. 2, a diagrammatic rendition of two systems, [VII] and [VIII], which are two-sheet systems.

The solid sensitizing materials are water-insoluble, and the capsules are water-dispersible.

DETAILED DESCRIPTION Example I The capsules of this sheet were made by the method disclosed in United States Pat. No. 2,800,457, which issued July 23, 1957, on the application of Barrett K. Green and Lowell Schleicher. In that invention, water-immiscible droplets of the selected dithiooxamide compound were dispersed in an aqueous dispersed coacervate of gelatin and gum arabic under agitation, whereby the droplets were coated with a complex of the gelatin and the gum arabic, which coating was set by cooling and rendered hard and water-insoluble by treatment with an aldehyde. The agitation was such as to give droplets of encapsulated liquid of about microns and walls of such thickness as to give a liquid content of 85 percent, by volume. These capsules were recovered and dispersed as a water slurry of percent solids with the metal salt to an amount of about 15 percent, by weight, dispersed therein. For this example, which is shown as [I] in FIG. 1, the autogenous type of sheet, the encapsulated material chosen is N,N' dioleyldithiooxamide, and the metal salt co-reactant chosen is Ni-dinonylnaphthalene sulfonate. The slurry is coated on a lb./ream (24 x 32 inches x 500 sheets) in an amount to leave a dried coating weight of two pounds per specified ream. This produces blackish-red marks on the event of a pressure pattern being applied by uninked type or other marking instrument.

Example II This is the sheet of FIG. 1 [II], wherein on the specified sheet there is first laid down a slurry-dispersion of the metal salt reactant and, when dried, over that is laid down a coating of the capsule slurry, to give a total of active material equivalent to that of Example I.

Example III In this example of an autogenous sheet, the layers as they appear in FIG. 1 [II] are reversed, so that the capsules rest directly on the substrate.

For the Examples [I], [II], and [III], the sheet preferably is paper, which is the record material of prime importance commercially, but it may be record film material, as the porosity of the sheet plays no significant part in the system.

Example IV In this example (FIG. 1 [IV] the metal salt in requisite amount is dispersed in the fibers of the paper machine furnish to yield a finished sheet of 30 pounds per ream plus several pounds per ream of the metal salt as an addition agent. On top of the finished sheet are coated the liquid-reactant-containing capsules in the amount of two pounds per specified ream, dry weight.

Example V In this example (FIG. 1 [V] the capsules are incorporated within a sheet of paper, preferably by the method disclosed in South African Pat. No. 827/66, in which the furnish fibers are sensitized with cationic starch and the capsules are applied as an aqueous slurry in a solution of Karaya gum at a point on the Fourdrinier machine directly onto the wet web of about 95 percent water content. Where the cationic and ionic materials meet, a coacervate is in- 4 stantaneously formed to hold the capsules within the upper thickness of the sheet.

The metal salt was applied to the surface of the sheet as a water dispersion or as -a methanol solution to leave the required residue.

Example VI In this example, diagrammatically rendered in FIG. 1 [VI], both reactants are buried within a paper sheet, a requisite amount of the metal salt being added to the slurry of capsules applied to the cationically-sensitized wet sheet in the process of formation.

Example VII In this example (FIG. 2 [VII] the over-sheet of paper has on its under surface a capsule coating including the liquid reactant in the amount of two pounds per specified ream, and the apposite paper under-sheet has on its top surface a chemically co-relative amount of one of the specified metal salts, no consideration being given to vapor pressure problems if the sheets are kept from storage contact before being put together for use and separated after use.

Example VIII In this example (FIG. 2 [VIII] the metal salt is incorporated within the body of the bottom sheet of a pair in the manner described in Example IV, and a chemically co-relative amount of capsules is applied to the apposite side of the over-sheet in the recommended two-pounds per-ream amount. These sheets should be placed together just before use and separated thereafter if the reactant in the capsules is a dithiooxamide having significant vapor pressure.

These Examples [I to VIII] are manifestations of utility of the central trust of the invention, which is the provision of marking-liquid-containing capsules whose entire content is a liquid compound which is reactant with a metal salt on contact to form an intensely-colored sludge. In the disclosed system, applied pressure ruptures the capsules in data image patterns to bring about the contact.

While the dithiooxamide compounds specified have been made from pure primary amine compound precursors producing compounds that are symmetrically substituted, it is within the scope of the invention that the dithiooxamide may be asymmetrically substituted by any alkyl groups and/or the alkenyl group noted in Examples [I] to [V], providing that the produced compound is liquid at temperatures specified for use.

Some commercially available amines are mixtures of alkyl amines and alkenyl amines, and their use without fractionation in synthesizing dithiooxamides may result in asymmetrically substituted products of the required liquid state at the specified temperatures and thus make them eligible for use in the practice of this invention.

The substituted dithiooxamides may be made by stirring two moles of the primary amine with one mole of the dithiooxamide in ethanol until the reaction takes place. The reaction product is recovered and purified if necessary.

What is claimed is:

1. A pressure-sensitive recording system comprising record sheet material which is marked by the sludge-like reaction product of a liquid dithiooxamide reactant compound coming into contact with a co-reacting solid compound reactant, said sheet material supporting both a multitude of microscopic pressure-rupturable capsules containing the liquid compound reactant material and in close apposition relation the solid co-reactant compound, the system being characterized by the absence of a diluent or liquid dispersing agent for the capsule-held reactant liquid compound whereby a distinctive colored sludge-like mark is made on the sheet material where marking pressure is applied to break the capsules and release the liquid re actant contents to make the contact where pressure is so applied.

2. The recording system of claim 1 wherein the solid co-reactant is a metal salt.

3. The recording system of claim 2 wherein the metal salt is taken from the group consisting of: Ni-dinonylnaphthalene sulfonate;

Cu-resinate;

Ni-resinate;

Cu-di (Z-ethylhexyl) phosphate; Ni-di (Z-ethylhexyl) phosphate; and Ni-stearate.

4. The recording system of claim 2 wherein the dithiooxamide is taken from the group consisting of: N,N'-dihexyl-dithiooxamide; N,N'-dipentyl-dithiooxamide; N,N'-dipropyl-dithiooxamide; N,N -dioctyl-dithiooxamide; and N,N-dioleyl-dithiooxamide.

5. A pressure-sensitive recording system comprising a substrate sheet of record material supporting, on a surface thereof, in a closely packed stratum, marking-pressure-rupturable microcapsules, each mierocapsule containing a liquid dithiooxamide color-reactant compound undiluted by solvent or dispersant, said sheet being for use with the capsule surface against a copy-receiving sheet of record material which is sensitized with a metallic salt, whereby marking pressure applied to the capsule-supporting sheet in data-representing image pattern will cause the liquid released from the pressure-ruptured capsules to be transferred to the copy-receiving sheet in the same pattern.

6. The system of claim 5 wherein the metal salt is one taken from the group consisting of:

Ni-dinonylnaphthalene sulfonate; Cu-resinate;

. croscopic droplets of reactant liquid retained isolated in pressure-rupturable film material distributed inclose relation in the sheet, said liquid being a dithiooxamide colorreactant compound without solvent or dispersant content.

References Cited UNITED STATES PATENTS 3,287,154 11/1966 Haas 1l7-36.2

3,427,180 2/1969 Phillips 1l7-36.2

2,929,736 3/1960 Miller et a1. 11736.9

FOREIGN PATENTS 1,042,599 9/1966 Great Britain 1l736.8

MURRAY KATZ, Primary Examiner US. Cl. X.R. 

